In the printing world, after artwork has been plotted onto a film, the artwork is transferred to a printing plate typically via a contact process. The printing plate is later to be placed on a printing press. In order to ensure that the artwork is registered properly on the material to be printed, the film must be properly registered on the printing plate.
In order to properly register the film on the printing plate, registration holes, corresponding to registration pins on the printing press and located outside of the area of the artwork, are punched out of the film prior to placing it on the printing plate.
A film which it is desired to cut is illustrated in FIG. 1 to which reference is now made. The page has artwork 8 around which are round holes 10 and oval holes 12 on the outer edges of the film, a line 13 indicating where the film should be cut to create two separate films and round holes 14 next to the line 13 for providing holes on the "inner" edges of the two separate films.
The punching can occur before or after placing the film into the plotter, or while the film is within the plotter.
For punching after the film has exited the plotter, a separate punch and die unit is typically utilized. Such units register the holes 10 or 12 with respect to the artwork 8 thereon either manually or via a cross-haired vision system.
If the holes are punched prior to plotting, the film, which has registration holes, is registered on the plotting surface (a drum or a flat surface) with registration pins which match the registration holes. The plotting of the artwork is then designed to be registered to the locations of the registration pins. However, there exist many types of films with many different types of holes and each plotter has a fixed and limited number of hole types to which it conforms.
Plotters which have hole punching units within them are also known. One such plotter, a punch and die unit formed within an external drum plotter, is described in Canadian Patent Publication A1-2,063,479 to Ben-David et al, incorporated herein by reference. Prior to plotting, the punch and die units are placed in desired locations and thereafter, the artwork 8 is formed on the film in precise registration with the location of the punch and die unit. Punching can occur at any appropriate time, before or after plotting.
The Background of '479 describes many other types of hole cutting systems which, therefore, will not be described herein.
The system described in '479 solves the problem of registration. However, it is inflexible and is only operative with one type of printing press.
Either of holes 10 and 12 can be produced by the system of '479, but not both by the same plotter. Holes 14 probably could be produced by the system of '479, but probably not by other types of systems.
A plotter having a punch and die unit similar to that described in '479 is useful for producing films for only a limited number of types of plates. As many print shops work with a plurality of printing presses, such a system is not practical.
It is noted that, after the holes 10-14 have been produced, the film is brought to a film cutter which separates the film into two films by cutting along line 13.